Traveling grate for flue-tube boilers



Feb. 21, 1939. Rl G|E5AU TRAVELING GRATE FOR FLUE-TUBE BOILERS Filed sept. 26)" 1936 Patented Feb. 21, 1939 PATENT OFFICE TRAVELING GRATE FOR FLUE-TUBE BOILERS Reinhold Giesau,

Dresden, Germany Application September 26, 1936, Serial No. 102,763

In Germany October 3, 1935 2 Claims.

Traveling grates for boiler furnaces have been designed up to now either as chain grates or as pushing grates. In the first of these cases the `individual grate plates are hinged to one another and constitute in this way an endless chain which runs over chain-wheels provided at the frontand at the rear of the grate path and being driven slowly along over the entire length of that path, the upper half of the endless chain or grate traveling, of course, from the lfront to the rear of the said path.

With pushing grates the individual grate plates follow one another loosely, without any connection between them, and the entire set is moved in ajerky manner, or intermittently, the plates on arriving at the rear end of the grate being withdrawn and returned below the grate to the front end thereof by means. specially provided for this purpose, the plates on arriving at the frontend of the grate being raised and fed forward again in the furnace.

Chain-grates in due-tube `boilers suffer from the drawback that the chain guide-Way narrows considerably the passage for the air; besides, said guide-way itself can only be narrow because otherwise the structure becomes too high in view of the diameter of the flue-tube which permits only a certain definite breadth of the grate structure. l

In the present improved construction constituting the present invention which relates to a pushing traveling grate, this grate is composed of individual movable plates coi-operating with lateral stationary grate portions whereby it is rendered possible to give the traveling portion of the grate a comparatively large breadth without reducing detrimentally the supply of air to the fuel. Furthermore, also the advantage is attained that a suiiicient amount of the fuel falls from the traveling middle portion of the grate upon said lateral grate portions.

It is also possible to blow in a simple manner compressed air or steam into the furnace, in that the members supporting and guiding the traveling middle grate portion are hollow and have at the inner face apertures for the introduction of the steam or the compressed air.

Another'feature of the invention resides therein that individual longitudinally movable grate bars provided with projections resembling ratchet-teeth are inserted between the lateral grate portions whereby it is rendered possible to convey the glowing fuel to any desired portion of the boiler and to conduct the combustion in such a manner as is necessary to produce the required amount of steam.

The invention is illustrated diagrammatically and by way of example on the accompanying drawing on which Figure 1 is a longitudinal section through a flame-tube provided with a pushing traveling grate designed according to this invention; Figure 2 is a transverse section in the plane 2-2 of Fig. 1; and Figures 3, 4 and 5 show three constructional forms of the above mentioned individual longitudinally movable lateral grate bars, all as dealt with in detail hereinafter.

On the drawing, w (Figs. l and 2) denotes the flue-tube which contains in its left-hand half and in its right-hand half longitudinally extending hollow bar-like members m having each an inwardly directed upper ilange or ledge m and an inwardly directed lower'ange or ledge m. In the example shown the upper ledges engage in the manner of feathers and grooves the oppositely located faces of the individual plates a of the traveling middle portion of the grate, but these plates are supported not only by said ledges or feathers, but also by rolls a." sup-ported on pivots projecting inwardly from said bar-like members m. The lower ledges m serve as supports and guides for the grate-bars a when these are moved in opposite direction into their initial position in order to be again rel-inserted into the flue.

At the rear of the furnace; behind the bars m and somewhat below them are supported angularly bent one-armed levers f on pivots g which canbe moved from the position shown in Fig. 1 in full lines into the position shown in dotted lines, and serve to receive and convey that grate plate a which is the last at the time being from the'upper guide ledge m to the lower guideledge m.

Between the ledges mf and a little below them are bars: o which are longitudinally movable and reciprocate while the plant is in operation. The means for moving said bars will be instantly described. Attached to the inner side of each of these bars are small double-armed levers p which are turnable on pivots p and are normally held in vertical position by abutment members p fixed to the bars o. The levers p can give Way only if the grate plates which have arrived `one after the other upon the edges m are moved in the direction to the front end of' the grate, i. e.lefthand in Fig. 1. 'I'he plates a are, at this time, located upon the bars o and are moved by them which is effected in a positive manner with the aid of upwardlydirected projections O (Fig- 1`) engaging that grate bar which lies most rearwards at the time being at its rear face. Y f On the bars o the` grate plates follow one another in the'direction from the rear to the front; `they are shoved over the upper arms of the levers p which now give way, but re-assume their former and proper vertical position immediately when the rear face of the grate plate concerned has passed away over Vthe levers p concerned, the

levers acting then as catches which shove the grate plate; in the direction to the front of the traveling grate when the bars o are moved to and fro.

The bars o are connected at their front ends with crank disks e supported on a shaft e by connecting rods I and are reciprocated thereby. On the same shaft and united with the disks e are cams k acting upon bell-crank levers h, of which one arm contacts with the appertainingl cam and the other arm is enlarged so as to form a plate, the object of which is to lift the grate plates a arriving at the front of the furnace from their lower position (on the bars o) to their proper upper position in which they can be shifted onto the ledges m of the hollow members m. This is effected by means of one-armed levers d supported on pivots d and reciprocated by means of the crank-disks with which they are connected by short connecting rods shown in dotted lines quite at the left-hand end of Fig. 1. The upper ends of said levers dy bear a horizontal slide b serving to shift the grate-plate lying upon the plate h onto the ledges-m whereby the grate plates already present upon these ledges are shifted forwards by as much as corresponds to the breadth of one grate plate (in the longitudinal direction of the flue). At the same time the grate plate at the rear of the grate is received by the now lifted arms of the lever f which carries that plate down to and upon the bars o in order to be conveyed back to the front of the furnace, as already described.

The lower arm of each lever p is equipped with a plate q by which the ashes are shoved from the rear to the front where they leave the ash-pit of the flue.

The middle portion of the grate which constitutes the traveling grate proper covers more than one half of the width of the flue-tube, or of the breadth of the entire grate respectively, whereby it is rendered possible to supply said middle portion of the grate with a comparatively large amount of fuel. The stationary lateral grate portions a.' are considerably narrower than the traveling grate portion whereby it is rendered possible to supply them with sufficient amounts of fuel by the intermediary of said traveling grate portion. Moreover, owing to the relatively narrow width of the lateral grate portions, the intermittent movement of the traveling grate portion on stopping holds by friction the entire moving bed of fuel. During this stoppage a certain amount of cementing or agglomeration of the fuel on the entire grate takes place but when movement of the traveling grate portion starts again this is broken along the linesy of separation between the traveling portion of the grate and the lateral grates. The fuel on the lateral grates is, however, carried on by friction though more slowly than the fuel on the traveling grate.

In order to conduct the combustion of the fuel particularly advantageously itis suitable to arrange between the stationary grate bars a' longitudinally movable grate-bars u (Figs. 3-5) which can be reciprocated manually by means of grips u (Fig. 1, left-hand end). These grate bars are provided on their upper face With projections 'v having a shape resembling the shape of ratchetteeth, and their number and arrangement depends on the sort of coal used, as well as upon the length and diameter of the ue tube. If it is thought proper to have the ignition zone located more in the centre portion of the grate relatively to the length of the same, grate-bars u with such teeth as in Fig. 3 are suited, in which case the teeth are distributed about over the front half and the rear half of the grate bar. It is then possible to direct the fuel onto the centre portion of the grate from the front-end, as well as from the rear end of the same. If this is to be effected more from the front end of the grate, the teeth o are positioned in the manner shown in Fig. 4, and if the fuel is to be directed to the central portion of the grate more from the rear end thereof, the teeth vare positioned in the manner shown in Fig. 5.

At the rear end of the grate, a little above it, is provided a scraper 1^ which retains the glowing fuel on the grate and distributes it laterally over the entire breadth of the grate.

From the slide b extends upwardly a pin or bolt t which lifts a iiap .r hinged to an axle located below the fuel feed hopper y. Said flap is lifted a little by said pin t when the slide b arrives at the end of its path in the direction to the grate, whereby choking up of the fuel in the hopper is prevented.

The bars m are hollow and provided on their inner sides with apertures n constituting nozzles through which air or steam can be blown into the furnace below the traveling portion of the grate.

I claim:

l. In a traveling grate for flue boilers, in combination a middle traveling grate portion and stationary grate portions located at both sides of and substantially at the same level as the middle grate portion, said stationary grate portions having longitudinally movable grate bars with ratchet-teeth like projections thereon interposed between stationary grate bars for enabling the fuel to be displaced for shifting the ignition zone of the fuel bed lengthwise of the grate.

2. In a traveling grate for flue-tube boilers, in combination, a middle grate portion consisting of individual grate plates, each of which is adapted to be separated at the end of its travel from the grate plates behind it, to be moved back into its initial position, and to be reinserted into the travel; means for intermittently driving said grate plates toward the rear of the furnace, lateral members for guiding said grate plates, members for receiving the individual separated plates, members for moving them back toward the front of the furnace, members for raising them to their initial position at the front,`and stationary grate portions located at both sides of the middle grate and at substantially the same level as the middle grate portion, the middle grate portion exceeding in width half the diameter of the flue-tube whereby the grate is adapted to produce a stoppage of the fuel over the width of the entire grate in stopping so that an agglomerated layer is formed, and in starting, a breaking of this layer and a forward movement of the fuel on the lateral portions of the grate at a slower rate than the fuel on the traveling portions of the grate.

REINHOLD GIESAU. 

